@PE, I'm not saying it's not happening. I'm saying it's where your efforts should focus, exclusively. Libertarians need a national figure with credibility, and you're not going to get that with presidential runs that aren't taken seriously. Even someone like Ross Perot, who did get a lot of votes, did not achieve anything sustainable for like-minded Americans (whatever ideology he espouses). Vanity runs at the presidency for symbolic or strategic ideological positioning do not help move political parties inside the Overton window. Twenty years later, the conventional wisdom takes Perot less seriously than it did in 1992. Twelve years later, we give Nader less credit than we did in 2000. Nobody remembers John Anderson.
@Tolstoy, "illegal" is the wrong word. You're not going to be jailed for being a member of a different party, unless America is a lot more Zimbabwe I thought. But most of your points speak get at what I was saying: focus on challenging ballot standards in state and local races, and getting the fundraising base you need to compete. That is how you will mount a credible challenge. Ross Perot is a poor example because he is a billionaire. I'm pretty sure most crazy billionaires could get the press to take them seriously.
But you are right that efforts to build a third party are probably unlikely to succeed even following this strategy, even if they're more likely to produce elected officials, because the American electoral system structurally favours two-party dominance. And that's where I would say you're probably even better off going the old-fashioned way (which, yes, I realize is happening) and just voting for guys like Rand Paul and getting like-minded people on the platform committee and running important candidates' campaigns. But aside from feeling better about your vote, I think support for third party candidates in presidential elections is unlikely to ever yield anything and comes with a significant credibility cost. So unless you really don't care who wins, I would vote for someone who can win.
Besides, if Gary Johnson gets more votes than Romney loses by, we will never know how many of them were Obama former supporters unhappy about NDAA or Gitmo or his policies on medical marijuana or drones or the assassination of American citizens or what have you. You can't get the kind symbolic or strategic ideological positioning through protest votes precisely because the meaning of those votes is always ambiguous. The conservatives in trust of the GOP will never concede that they are losing votes because they are too hawkish on foreign policy or too tough on crime or drugs or terrorism.